The current state of the art of which I am aware for controlling the infinitely variable intensity of light within a space, (either ambient light or accent light, such as theatrical lighting) is to use a phase fired dimmer to chop the sign wave voltage and supply the fixture or lamp with a voltage varying from 0 volts to 120 volts. The single light source in the fixture is then controlled over the range from off to full bright. In operation, this is a dimmer control. By varying the voltage supplied to the light source; therefore, the light output level of the fixture is varied. There is a need in the art to control the light output level of a fixture by controlling individual light sources in the fixture without varying the voltage supplied to the fixture; more particularly, there is a need to control individual light sources of a constant voltage source light fixture.
The current technology to dim a fixture varies the voltage by using a phase fired silicon controlled rectifier (SCR) dimmer. The voltage is supplied to a single filament or light source and the light output level increases in intensity as the voltage and current rise. One particular drawback of these systems is electromagnetic interference (EMI) and radio frequency interference (RFI) generated by the SCR dimmer. EMI and RFI are generated by the SCR dimmer even when using a torroidal choke on the output of the dimmer. Therefore, there is a need in the art to eliminate the EMI and RFI generated by a light fixture, and more particularly, there is a need in the art to eliminate the EMI and RFI generated by varying the light output level of a light fixture.
New United States energy code requirements as of this writing will require all lighting output in public buildings to be controllable to at least two levels to meet the energy saving requirements of the energy code. Existing buildings not conforming to the code will require installation of new wires to fixtures and splitting the ballasts and light sources within the fixtures into two separate circuits. Thus, there is a need in the art to ease the retrofitting of existing fixtures to obtain at least two different levels of light output.
Typically, it is standard practice to provide two different power feeds to a fixture to obtain two levels of lighting. Providing two different power feeds to a fixture is more expensive and requires additional line voltage field wiring to remote switches in order to operate. Therefore, there is a need in the art to enable a fixture to obtain at least two levels of lighting using a single power feed. Further, additional wiring is required to remotely control additional fixtures and for controlling the two lighting levels. Therefore, there is a need in the art to network light fixture control.